Lessons learned from the decommissioning of nuclear facilities and the safe termination of nuclear activities: proceedings of an international conference on lessons learned from the decommissioning of nuclear facilities and the safe termination of nuclear activities organized by the International Atomic Energy Agency, co-sponsored by the European Commission, in cooperation with the OECD Nuclear Energy Agency and the World Nuclear Association, hosted by the Government of Greece through the Ministry of Foreign Affairs of the Hellenic Republic and the Greek Atomic Energy Commission and held in Athens, 11―15 December 2006